The invention relates to a method for measuring a fluid level through determining an inclination angle of a bracket that rotatably interconnects a floating member located near a surface of the fluid level to a pivoting arrangement, which carries a resistor facility of which a part is branched off through a slider that is moving along with a change in said angle.
The accurately determining of a fluid level in a container is of great importance in various environments, such as in particular, but not limited to, gasoline tanks in motor vehicles. The measurement arrangement must fulfill many and sometimes contradicting requirements. It must be inexpensive, be nearly insensitive against appreciable accelerations in all directions of the vehicle, both static and dynamic, must present no fire hazards in an environment with large volumes of highly combustible matter, and so on. Therefore, if such measurement is executed in an electrical manner, any voltages used must be as low as feasible. In practice, the measuring has been executed through measuring a variable resistance which will change under influence of the fluid level through the motion of the slider along a resistor track such as one executed in thick film technology. The mechanical aspects of such arrangement have been disclosed in U.S. Pat. No. 6,267,007 B1 assigned to Mannesmann VDO AG.
The measuring of the angle, and indirectly, of the remaining fluid content, therefore boils down to the measuring of a resistance value, one end of the resistor being connected in a fixed manner, and the sliding in effect constituting a moving contact. Two-wire measuring of such resistance value requires a measuring current to run through the sliding contact, so that the contact resistance may influence the measuring accuracy in an adverse manner. Moreover, the contact resistance may even on a short timescale vary over a wide range.
In consequence, amongst other things, it is an object of the present invention to diminish the value of the measuring current through the contact resistance, while furthermore providing an arrangement that allows to eliminate any influence of the contact resistance to an allowable low level.